Hi,
We are studying an aquifers beneath an iron mine pit. Actually, we want to know the direction of water flow in the subsurface for future Maintenance plans of the mine pit. More precisely, by knowing the flow direction, controlling wells will be drilled to prevent of the penetration of water in the mine.
We are employing a 3D geoelectric resistivity project to map the subsurface water table. I am wondering if there exist a hydrogeological software (code or method) to investigate the water flow direction from the obtained 3D map of water table (which itself obtained by resistivity map) in subsurface?
I would think that MODFLOW would work. It is a 3D finite-difference groundwater modeling program developed by the USGS and is freely available.
Hi，Hamzeh,
As a matter of fact, 3D geoelectrical resistivity section is a very useful tool in groundwater and geothermal rservoir investigation. You can find plenty of examples in the literature. From our experience, we feel that the following are important points in practice: 1，It is more effective when integrated with structural geological information if not guided by geological theories before the resistivity measurements take place; 2, Interpretation could be misled by complex geological factors so it is ideal to cross check with information generated by techniques that are not influenced by resistivity. Methods available include soil CO2, Soil Radon, and so on...
Hope this is useful to you. Good luck!
Hello Hamzeh,
Please let me know if I understand correctly: You would like to use the water depths estimated from your 3D resistivity survey to determine groundwater flow direction?
While this is possible, it would require a very well controlled survey. My concern would be that the groundwater table elevation will vary less than the resolution of the electrical resistivity data. Which means any attempt at determining groundwater flow direction would be meaningless. This will be a direct result of the electrode "a" spacing and spatial survey extent relative to groundwater depth. However, if conditions are optimal, i.e the gradient is steep, the geology is relatively resistive and homogenous, and the electrodes are surveyed within +/- 2cm there is a possibility this could be successful. It would be much better if there were existing borings to use for ground truth, as well.
As far as actually modeling direction, once you've identified your depths/elevations and associated coordinates, you would simply put them into any contouring program. MODFLOW should also work as suggested above.
I'd be interested see your results.
Best of luck.
Dear Danney,
Thank you for your comprehensive explanation.
Yes, you're right. this is the case.
The electrode spacing is 2000m. The total survey area is about 8.13 km^2, and is approximately the square shaped. The estimated water table is around 200m in depth, but we study more than 300m depth. Taking all these into account what is your analysis?
Best Regards.
Dear Dr. Hamzeh,
If the 3D resistivity survey has reached to the aquifer bottom at some points of your area , you could calculate the Dar-Zarrouk parameters for your aquifer and one of them is longitudinal conductance which might be used to detect the flowing directions of groundwater.
hope this will help.
Best Regards.
Wadhah
This geoelectrical imaging technique was used along profile using the 3-D pole-pole survey to declare the condition of resistivity distribution horizontally and vertically with depth in the water-bearing fractured limestone as example. The pole-pole electrode configuration is commonly used for 3-D surveys, such as the ESCAN method (Li and Oldenburg 1992). The electrodes for 3-D surveys are normally arranged in a rectangular grid with a constant spacing between the electrodes
You can use also pol-dipol method with twin dipolimagine to see the flow direction.
Your research is also good.
During work in harvesting rainfall as example, we need to know the subserface condition for cistern location.thus 3D imagine techniqes used.
Also this techniqe is good for detecting structures that affect on groundwater occurrence
We have use also the IP method in order to determine correctly all the water levels only till 100 meters, sedimentary or other rocks.
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